Nitrate in groundwater of China: Sources and driving forces

Identifying the sources of reactive nitrogen (N) and quantifying their contributions to groundwater nitrate concentrations are critical to understanding the dynamics of groundwater nitrate contamination. Here we assessed groundwater nitrate contamination in China using literature analysis and N balance calculation in coupled human and natural systems. The source appointment via N balance was well validated by field data via literature analysis. Nitrate was detected in 96% of groundwater samples based on a common detection threshold of 0.2 mg N L^?1, and 28% of groundwater samples exceeded WHO's maximum contaminant level (10 mg N L^?1). Groundwater nitrate concentrations were the highest beneath industrial land (median: 34.6 mg N L^?1), followed by urban land (10.2 mg N L^?1), cropland (4.8 mg N L^?1), and rural human settlement (4.0 mg N L^?1), with the lowest found beneath natural land (0.8 mg N L^?1). During the period 1980–2008, total reactive N leakage to groundwater increased about 1.5 times, from 2.0 to 5.0 Tg N year^?1, in China. Despite that the contribution of cropland to the total amount of reactive N leakage to groundwater was reduced from 50 to 40% during the past three decades, cropland still was the single largest source, while the contribution from landfill rapidly increased from 10 to 34%. High reactive N leakage mainly occurred in relatively developed agricultural or urbanized regions with a large population. The amount of reactive N leakage to groundwater was mainly driven by anthropogenic factors (population, gross domestic product, urbanization rate and land use type). We constructed a high resolution map of reactive N source appointment and this could be the basis for future modeling of groundwater nitrate dynamics and for policy development on mitigation of groundwater contamination.     

A minimal model for wind- and mixing-driven overturning: threshold behavior for both driving mechanisms

We present a minimal conceptual model for the Atlantic meridional overturning circulation which incorporates the advection of salinity and the basic dynamics of the oceanic pycnocline. Four tracer transport processes following Gnanadesikan in Science 283(5410):2077–2079, (1999) allow for a dynamical adjustment of the oceanic pycnocline which defines the vertical extent of a mid-latitudinal box. At the same time the model captures the salt-advection feedback (Stommel in Tellus 13(2):224–230, (1961)). Due to its simplicity the model can be solved analytically in the purely wind- and purely mixing-driven cases. We find the possibility of abrupt transition in response to surface freshwater forcing in both cases even though the circulations are very different in physics and geometry. This analytical approach also provides expressions for the critical freshwater input marking the change in the dynamics of the system. Our analysis shows that including the pycnocline dynamics in a salt-advection model causes a decrease in the freshwater sensitivity of its northern sinking up to a threshold at which the circulation breaks down. Compared to previous studies the model is restricted to the essential ingredients. Still, it exhibits a rich behavior which reaches beyond the scope of this study and might be used as a paradigm for the qualitative behaviour of the Atlantic overturning in the discussion of driving mechanisms.     

Dynamic adaptive policy pathways: A method for crafting robust decisions for a deeply uncertain world

A new paradigm for planning under conditions of deep uncertainty has emerged in the literature. According to this paradigm, a planner should create a strategic vision of the future, commit to short-term actions, and establish a framework to guide future actions. A plan that embodies these ideas allows for its dynamic adaptation over time to meet changing circumstances. We propose a method for decisionmaking under uncertain global and regional changes called ‘Dynamic Adaptive Policy Pathways’. We base our approach on two complementary approaches for designing adaptive plans: ‘Adaptive Policymaking’ and ‘Adaptation Pathways’. Adaptive Policymaking is a theoretical approach describing a planning process with different types of actions (e.g. ‘mitigating actions’ and ‘hedging actions’) and signposts to monitor to see if adaptation is needed. In contrast, Adaptation Pathways provides an analytical approach for exploring and sequencing a set of possible actions based on alternative external developments over time. We illustrate the Dynamic Adaptive Policy Pathways approach by producing an adaptive plan for long-term water management of the Rhine Delta in the Netherlands that takes into account the deep uncertainties about the future arising from social, political, technological, economic, and climate changes. The results suggest that it is worthwhile to further test and use the approach.     

面向智能驾驶视觉感知的对抗样本攻击与防御方法综述

现如今,深度学习已然成为机器学习领域最热门的研究方向之一,其在图像识别、目标检测、语音处理、问答系统等诸多领域都取得了巨大成功.然而通过附加经过特殊设计的细微扰动而构造出的对抗样本,能够破坏深度模型的原有性能,其存在使许多对安全性能指标具有极高要求的技术领域,特别是以视觉感知为主要技术优先的智能驾驶系统,面临新的威胁和挑战.因此,对对抗样本的生成攻击和主动防御研究,成为深度学习和计算机视觉领域极为重要的交叉性研究课题.本文首先简述了对抗样本的相关概念,在此基础上详细介绍了一系列典型的对抗样本攻击和防御算法.随后,列举了针对视觉感知系统的多个物理世界攻击实例,探讨了其对智能驾驶领域的潜在影响.最后,对对抗样本的攻击与防御研究进行了技术展望.     

Socio-economic driving forces of arable land conversion: A case study of Wuxian City,China

This research examines the impact of the farmland protection policy institutionalized for China's paddy field conversion in the mid-1990s. This paper demonstrates an integrated research method for studying land use-cover changes from the perspective of the interactions between policy changes and socioeconomic factors. The integrated method deploys remote sensing to obtain accurate measures of paddy field changes and applies multiple regression analysis to explore the interactions between paddy field change and socioeconomic factors. It constructs a policy-determined categorical regression analysis to investigate whether the policy change impacts paddy field conversion and how the policy interacts with other socioeconomic factors in affecting paddy field losses. A geographic information system is deployed to interpret the spatial patterns of the interactions. The case study in Wuxian City (Jiangsu Province) concludes that there is a distinct policy shift between 1990–1995 and 1995–2000. The policy of regulating farmland losses practiced in the mid-1990s has a significant role of slowing down paddy field conversion. But the success has been partial and was largely compromised in the rural areas due to the compounding forces of policies to promote rapid economic growth and better living standards. Moreover, continued rural to urban migration, rural economic development and rapid urban expansion represent the primary forces that lead to the conversion of paddy fields into non-agricultural uses.     

Solar wind: A possible factor driving the interannual sea surface temperature tripolar mode over North Atlantic

The effect of solar wind (SW) on the North Atlantic sea surface temperature (SST) in boreal winter is examined through an analysis of observational data during 1964-2013. The North Atlantic SSTs show a pronounced meridional tripolar pattern in response to solar wind speed (SWS) variations. This pattern is broadly similar to the leading empirical orthogonal function (EOF) mode of interannual variations in the wintertime SSTs over North Atlantic. The time series of this leading EOF mode of SST shows a significant interannual period, which is the same as that of wintertime SWS. This response also appears as a compact north-south seesaw of sea level pressure and a vertical tripolar structure of zonal wind, which simultaneously resembles the North Atlantic Oscillation (NAO) in the overlying atmosphere. As compared with the typical low SWS winters, during the typical high SWS winters, the stratospheric polar night jet (PNJ) is evidently enhanced and extends from the stratosphere to the troposphere, even down to the North Atlantic Ocean surface. Notably, the North Atlantic Ocean is an exclusive region in which the SW signal spreads downward from the stratosphere to the troposphere. Thus, it seems that the SW is a possible factor for this North Atlantic SST tripolar mode. The dynamical process of stratosphere-troposphere coupling, together with the global atmospheric electric circuit-cloud microphysical process, probably accounts for the particular downward propagation of the SW signal.     

Transaction costs for firms in the EU ETS: lessons from Ireland

Until now, there has been little empirical evidence that EU Emissions Trading Scheme (ETS) transaction costs are incurred at firm level. The transaction costs (internal costs, capital costs, consultancy and trading costs) incurred by Irish firms under the EU ETS during its pilot phase (2005–2007) were measured and analysed. Evidence for the sources of transaction costs, their magnitude and the distribution of costs shows that these were mainly administrative in nature. Considerable variation in costs was found due to economies of scale, as the costs per tonne of CO₂ were lower for participants with larger allocations. For the largest firms—accounting for over half the emissions—average transaction costs were €0.05 per tonne. However, for small firms, average transaction costs were €2.02—over 18% of the current allowance price. This supports the concerns that transaction costs are excessive for smaller participants. The immediate policy implication is that additional attention will be needed to address different sizes of firms, number of installations per firm, and the size of the initial allocations.     

Nationalizing a global phenomenon: A study of how the press in 45 countries and territories portrays climate change

This study investigates the news coverage of climate change in 45 different countries and territories. Using the news framing approach, this study identifies the connections between several national socioeconomic, governance, and environmental traits and the portrayals of climate change. Although climate change is a global issue that affects every country in the world, how the news media frame it varies from country to country. Such a variation is related to each country’s economic development, climate severity, and governance. The findings of this study contribute to framing literature by assessing frame use in national contexts, filling in the gap in the application of this theoretical framework.     

The role of carbon plantations in mitigating climate change: potentials and costs

A methodology is presented to construct supply curves and cost–supply curves for carbon plantations based on land-use scenarios from the Integrated Model to Assess the Global Environment (IMAGE 2). A sensitivity analysis for assessing which factors are most important in shaping these curves is also presented. In the IPCC SRES B2 Scenario, the carbon sequestration potential on abandoned agricultural land increases from 60 MtC/year in 2010 to 2,700 MtC/year in 2100 for prices up to 1,000 $/tC, assuming harvest when the mean annual increment decreases and assuming no environmental, economical or political barriers in the implementation-phase. Taking these barriers into consideration would reduce the potential by at least 60%. On the other hand, the potential will increase 55 to 75% if plantations on harvested timberland are considered. Taking into account land and establishment costs, the largest part of the potential up to 2025 can be supplied below 100 $/tC (In this article all dollar values are in US dollars of 1995, unless indicated otherwise.). Beyond 2050, more than 50% of the costs come to over 200 $/tC. Compared to other mitigation options, this is relative cheap. So a large part of the potential will likely be used in an overall mitigation strategy. However, since huge emission reductions are probably needed, the relative contribution of plantations will be low (around 3%). The largest source of uncertainty with respect to both potentials and costs is the growth rate of plantations compared to the natural vegetation.     

Assessing the robustness of adaptation decisions to climate change uncertainties: A case study on water resources management in the East of England

Projections of future climate change are plagued with uncertainties, causing difficulties for planners taking decisions on adaptation measures. This paper presents an assessment framework that allows the identification of adaptation strategies that are robust (i.e. insensitive) to climate change uncertainties. The framework is applied to a case study of water resources management in the East of England, more specifically to the Anglian Water Services’ 25 year Water Resource Plan (WRP). The paper presents a local sensitivity analysis (a ‘one-at-a-time’ experiment) of the various elements of the modelling framework (e.g., emissions of greenhouse gases, climate sensitivity and global climate models) in order to determine whether or not a decision to adapt to climate change is sensitive to uncertainty in those elements.Water resources are found to be sensitive to uncertainties in regional climate response (from general circulation models and dynamical downscaling), in climate sensitivity and in climate impacts. Aerosol forcing and greenhouse gas emissions uncertainties are also important, whereas uncertainties from ocean mixing and the carbon cycle are not. Despite these large uncertainties, Anglian Water Services’ WRP remains robust to the climate change uncertainties sampled because of the adaptation options being considered (e.g. extension of water treatment works), because the climate model used for their planning (HadCM3) predicts drier conditions than other models, and because ‘one-at-a-time’ experiments do not sample the combination of different extremes in the uncertainty range of parameters. This research raises the question of how much certainty is required in climate change projections to justify investment in adaptation measures, and whether such certainty can be delivered.     

Future changes in daily summer temperature variability: driving processes and role for temperature extremes

Anthropogenic greenhouse gas emissions are expected to lead to more frequent and intense summer temperature extremes, not only due to the mean warming itself, but also due to changes in temperature variability. To test this hypothesis, we analyse daily output of ten PRUDENCE regional climate model scenarios over Europe for the 2071–2100 period. The models project more frequent temperature extremes particularly over the Mediterranean and the transitional climate zone (TCZ, between the Mediterranean to the south and the Baltic Sea to the north). The projected warming of the uppermost percentiles of daily summer temperatures is found to be largest over France (in the region of maximum variability increase) rather than the Mediterranean (where the mean warming is largest). The underlying changes in temperature variability may arise from changes in (1) interannual temperature variability, (2) intraseasonal variability, and (3) the seasonal cycle. We present a methodology to decompose the total daily variability into these three components. Over France and depending upon the model, the total daily summer temperature variability is projected to significantly increase by 20–40% as a result of increases in all three components: interannual variability (30–95%), seasonal variability (35–105%), and intraseasonal variability (10–30%). Variability changes in northern and southern Europe are substantially smaller. Over France and parts of the TCZ, the models simulate a progressive warming within the summer season (corresponding to an increase in seasonal variability), with the projected temperature change in August exceeding that in June by 2–3 K. Thus, the most distinct warming is superimposed upon the maximum of the current seasonal cycle, leading to a higher intensity of extremes and an extension of the summer period (enabling extreme temperatures and heat waves even in September). The processes driving the variability changes are different for the three components but generally relate to enhanced land–atmosphere coupling and/or increased variability of surface net radiation, accompanied by a strong reduction of cloudiness, atmospheric circulation changes and a progressive depletion of soil moisture within the summer season. The relative contribution of these processes differs substantially between models.     

Quantifying how climatic factors affect variation in plant disease severity: A general method using a new way to analyze meteorological data

A general method is presented for analyzing how climatic conditions affect plant disease severity. An example of its application is given for the analysis of stripe rust (caused by Puccinia striiformis) data on winter wheat cultivar Gaines and climatic data collected at Pullman, WA. for 1968–1986. A computer program WINDOW was written to identify the climatic factors most highly correlated with disease. This program is designed to utilize meteorological data for an entire growing season of a crop as well as to include climatic conditions preceding planting. This program uses an iterative process to examine variable-length segments of meteorological data in a more exhaustive analysis than previously possible. Climatic factors considered include: mean maximum, minimum, and average temperature; total and frequency of precipitation; consecutive days with and without precipitation; accumulation of negative and positive degree days; and number of days with extreme temperature events. Variables that were highly correlated with disease were the basis for regression models that were developed to predict disease severity index for each of the three cultivars. Two- and three-variable models explained, respectively, 75 and 76% of the variation in disease from year to year. Predictions (which could be made early enough in the growing season to allow application of chemical control) were evaluated on the basis of whether years with severe disease were accurately predicted. Models were validated using Allen's PRESS statistic and by application to new data. The method is potentially applicable to studies of how climatic conditions affect the populations or productivity of other types of organisms.This research was supported by a National Science Foundation Grant (ATM 85-03115), Climate Dynamics Program, Division of Atmospheric Sciences.     

Carbon reduction in the real world: how the UK will surpass its Kyoto obligations

Abstract

Carbon dioxide emissions from UK energy use have fallen by more than 20% over the last 30 years, and carbon intensity—carbon emissions per unit of GDP—has halved. These reductions have been achieved by a combination of decarbonisation of the energy system and substantial improvements in energy efficiency. Use of natural gas in power generation has been a big factor in recent years, but energy efficiency improvements in households and particularly industry have been more important over a longer period. Government policies designed primarily to address climate change have not been important contributors, until recently.

Future reductions in emissions will require more proactive policies. However, they are possible without any economic difficulties, notably by adopting cost-effective energy efficiency measures, using new renewable energy sources and reducing dependence on private cars. These policies will improve economic efficiency. The new UK Climate Change Programme includes policies that combine regulation, investment, fiscal measures and other economic instruments. By working with the grain of other social, environmental and economic policies, they can achieve far more than a carbon tax alone, set at any politically acceptable level. Modelling the costs of emission reductions using a carbon tax as the only instrument would not only massively over-estimate costs, it would bear little resemblance to real world politics.

The paper demonstrates that a more diverse set of policy instruments is likely to be an effective and politically acceptable approach in a mature industrial economy. It is concluded that the UK's Kyoto target of a 12.5% reduction in greenhouse gas emissions is not challenging. The UK Government's target of reducing carbon dioxide emissions by 20% between 1990 and 2010 is also achievable. By 2010 per capita emissions from the UK will be well below 2.5 tC per year. Claims that some countries, notably the USA, could not reduce per capita emissions below 6 tC per year seem inconsistent with this experience.     

Carbon reduction in the real world: how the UK will surpass its Kyoto obligations

Carbon dioxide emissions from UK energy use have fallen by more than 20% over the last 30 years, and carbon intensity — carbon emissions per unit of GDP — has halved. These reductions have been achieved by a combination of decarbonisation of the energy system and substantial improvements in energy efficiency. Use of natural gas in power generation has been a big factor in recent years, but energy efficiency improvements in households and particularly industry have been more important over a longer period. Government policies designed primarily to address climate change have not been important contributors, until recently.Future reductions in emissions will require more proactive policies. However, they are possible without any economic difficulties, notably by adopting cost-effective energy efficiency measures, using new renewable energy sources and reducing dependence on private cars. These policies will improve economic efficiency. The new UK Climate Change Programme includes policies that combine regulation, investment, fiscal measures and other economic instruments. By working with the grain of other social, environmental and economic policies, they can achieve far more than a carbon tax alone, set at any politically acceptable level. Modelling the costs of emission reductions using a carbon tax as the only instrument would not only massively over-estimate costs, it would bear little resemblance to real world politics.The paper demonstrates that a more diverse set of policy instruments is likely to be an effective and politically acceptable approach in a mature industrial economy. It is concluded that the UK’s Kyoto target of a 12.5% reduction in greenhouse gas emissions is not challenging. The UK Government’s target of reducing carbon dioxide emissions by 20% between 1990 and 2010 is also achievable. By 2010 per capita emissions from the UK will be well below 2.5 tC per year. Claims that some countries, notably the USA, could not reduce per capita emissions below 6 tC per year seem inconsistent with this experience.     

Protected areas as a double edge sword: An analysis of factors driving urbanisation in their surroundings

Protected areas (PAs) are the most effective tools to protect biodiversity and ecosystem services. They have proven to be effective in stopping extensive land use conversion in well-conserved terrestrial ecosystems. However, land cover changes around PAs threaten biodiversity and ecosystem services within their limits and reduce ecological connectivity. In this study, we analysed the urban sprawls on the boundaries of 159 PAs (national, regional, and natural parks) in Spain, using 2.5 and 5 km non-protected buffer zones from 1990 to 2018. We clustered PAs based on biophysical and socio-economic characteristics and modelled urban sprawl in different buffers and periods. Hierarchical clustering revealed three groups of PAs: (a) proximate urban parks, (b) mountainous parks, and (c) parks in the Madrid autonomous region. We found that urbanisation in the surroundings of PAs in Spain has nearly doubled since 1990. General linear models explained a significant proportion of the urbanisation trends observed, with the number of municipalities in the boundary of the PA, the distance to a main road, and the distance to a big city acting as the most important drivers of urban sprawl. Our results also show that some PAs exert significant effects on urbanisation trends in their surroundings through the park-view effect. Finally, we highlight three coexisting phenomena that might explain the observed urban sprawl processes: (a) PAs attracting urbanisation in their surroundings due to the park-view effect, (b) PAs as a deterrent for urban sprawl within their limits, and (c) PAs occupying residual areas among previously urbanised lands.     

European climate in the late twenty-first century: regional simulations with two driving global models and two forcing scenarios

A basic analysis is presented for a series of regional climate change simulations that were conducted by the Swedish Rossby Centre and contribute to the PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change risks and Effects) project. For each of the two driving global models HadAM3H and ECHAM4/OPYC3, a 30-year control run and two 30-year scenario runs (based on the SRES A2 and B2 emission scenarios) were made with the regional model. In this way, four realizations of climate change from 1961–1990 to 2071–2100 were obtained. The simulated changes are larger for the A2 than the B2 scenario (although with few qualitative differences) and in most cases in the ECHAM4/OPYC3-driven (RE) than in the HadAM3H-driven (RH) regional simulations. In all the scenario runs, the warming in northern Europe is largest in winter or late autumn. In central and southern Europe, the warming peaks in summer when it locally reaches 10 °C in the RE-A2 simulation and 6–7 °C in the RH-A2 and RE-B2 simulations. The four simulations agree on a general increase in precipitation in northern Europe especially in winter and on a general decrease in precipitation in southern and central Europe in summer, but the magnitude and the geographical patterns of the change differ markedly between RH and RE. This reflects very different changes in the atmospheric circulation during the winter half-year, which also lead to quite different simulated changes in windiness. All four simulations show a large increase in the lowest minimum temperatures in northern, central and eastern Europe, most likely due to reduced snow cover. Extreme daily precipitation increases even in most of those areas where the mean annual precipitation decreases.     

Climate change and river floods in the European Union: Socio-economic consequences and the costs and benefits of adaptation

This study presents the first appraisal of the socio-economic impacts of river floods in the European Union in view of climate and socio-economic changes. The assessment is based on two trajectories: (a) no adaptation, where the current levels of protection are kept constant, and (b) adaptation, where the level of protection is increased to defend against future flooding events. As a basis for our analysis we use an ensemble-based pan-European flood hazard assessment for present and future conditions. Socio-economic impacts are estimated by combining flood inundation maps with information on assets exposure and vulnerability. Ensemble-based results indicate that current expected annual population affected of ca. 200,000 is projected to increase up to 360,000 due to the effects of socio-economic development and climate change. Under the no adaptation trajectory current expected annual damages of €5.5 billion/year are projected to reach €98 billion/year by the 2080s due to the combined effects of socio-economic and climate change. Under the adaptation trajectory the avoided damages (benefits) amount to €53 billion/year by the 2080s. An analysis of the potential costs of adaptation associated with the increase in protection suggests that adaptation could be highly cost-effective. There is, however, a wide range around these central numbers reflecting the variability in projected climate. Analysis at the country level shows high damages, and by association high costs of adaptation, in the United Kingdom, France, Italy, Romania, Hungary and Czech Republic. At the country level, there is an even wider range around these central values, thus, pointing to a need to consider climate uncertainty in formulating practical adaptation strategies.     

The fate of Lake Baikal: how climate change may alter deep ventilation in the largest lake on Earth

Lake Baikal is the oldest, deepest, and most voluminous freshwater lake on Earth. Despite its enormous depth, episodically (almost twice a year) large amounts of surface, cold, and oxygenated water sink until the bottom of the lake due to thermobaric instability, with consequent effects on the ecology of the whole lake. A minimal one-dimensional model is used to investigate how changes in the main external forcing (i.e., wind and lake surface temperature) may affect this deep ventilation mechanism. The effect of climate change is evaluated considering the IPCC RCP8.5 and some idealized scenarios and is quantified by (i) estimating the mean annual downwelling volume and temperature and (ii) analyzing vertical temperature and dissolved oxygen profiles. The results suggest that the strongest impact is produced by alterations of wind forcing, while deep ventilation is resistant to rising lake surface temperature. In fact, the seasons when deep ventilation can occur can be shifted in time by lake warming, but not dramatically modified in their duration. Overall, the results show that Lake Baikal is sensible to climate change, to an extent that the ecosystem and water quality of this unique lacustrine system may undergo profound disturbances.     

Atmospheric circulation in regional climate models over Central Europe: links to surface air temperature and the influence of driving data

The study examines simulation of atmospheric circulation, represented by circulation indices (flow direction, strength and vorticity), and links between circulation and daily surface air temperatures in regional climate models (RCMs) over Central Europe. We explore control simulations of five high-resolution RCMs from the ENSEMBLES project driven by re-analysis (ERA-40) and the same global climate model (ECHAM5 GCM) plus of one RCM (RCA) driven by different GCMs. The aims are to (1) identify errors in RCM-simulated distributions of circulation indices in individual seasons, (2) identify errors in simulated temperatures under particular circulation indices, and (3) compare performance of individual RCMs with respect to the driving data. Although most of the RCMs qualitatively reflect observed distributions of the airflow indices, each produces distributions significantly different from the observations. General biases include overestimation of the frequency of strong flow days and of strong cyclonic vorticity. Some circulation biases obviously propagate from the driving data. ECHAM5 and all simulations driven by ECHAM5 underestimate frequency of easterly flow, mainly in summer. Except for HIRHAM, however, all RCMs driven by ECHAM5 improve on the driving GCM in simulating atmospheric circulation. The influence on circulation characteristics in the nested RCM differs between GCMs, as demonstrated in a set of RCA simulations with different driving data. The driving data control on circulation in RCA is particularly weak for the BCM GCM, in which case RCA substantially modifies (but does not improve) the circulation from the driving data in both winter and summer. Those RCMs with the most distorted atmospheric circulation are HIRHAM driven by ECHAM5 and RCA driven by BCM. Relatively strong relationships between circulation indices and surface air temperatures were found in the observed data for Central Europe. The links differ by season and are usually stronger for daily maxima than minima. RCMs qualitatively reproduce these relationships. Effects of the driving model biases were found on RCMs’ performance in reproducing not only atmospheric circulation but also the links to surface temperature. However, the RCM formulation appears to be more important than the driving data in representing the latter. Differences of the circulation-to-temperature links among the RCA simulations are smaller and the links tend to be more realistic compared to the driving GCMs.     

The (ir)relevance of transaction costs in climate policy instrument choice: an analysis of the EU and the US

This article assesses the relevance of ex post transaction costs in the choice of climate policy instruments in the EU (focusing mainly on the example of Germany) and the US. It reviews all publicly available empirical ex post transaction cost studies of climate policy instruments broken down by the main private and public sector cost factors and offers hypotheses on how these factors may scale depending on instrument design and other contextual factors. The key finding from the evaluated schemes is that it is possible to reject the hypothesis that asymmetries in ex post transaction costs across instruments are large and, thus, play a pivotal role in climate policy instrument choice. Both total and relative ex post transaction costs can be considered low. This conjecture differs from the experience in other areas of environmental policy instruments where high total transaction costs are considered to be important factors in the overall assessment of optimal environmental policy choice. Against this background, the main claim of this article is that in climate policy instrument choice, ex post transaction cost considerations play a minor role in large countries that feature similar institutional characteristics as the EU and the US. Rather, the focus should be on the efficiency properties of instruments for incentivizing abatement, as well as equity and political economy considerations (and other societally relevant objectives). In order to inform transaction cost considerations in climate policy instrument choice in countries that adopt new climate policies, more data would be desirable in order to enable more robust estimates of design- and context-specific transaction-cost scaling factors.

Policy relevance

The findings of this study can help inform policy makers who plan to set up novel climate policy instruments. The results indicate that ex post transaction costs play a minor role for large countries that feature similar institutional characteristics as the EU and the US. For instrument design the focus should rather be on efficiency properties of instruments in incentivizing abatement, as well as equity and political economy considerations (and other societally relevant objectives).